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What is Leptospirosis?

Picture of  Leptospirae

Leptospirosis is a bacterial disease of dogs and other mammals that primarily affects the liver or kidneys.  Leptospires are known as "aquatic spirochetes": the organism thrives in water and they have a helical or spiral shape with a characteristic hook on one or both ends.  There is no evidence that Leptospirosis causes clinical disease in cats.


How are dogs infected?

Most dogs are infected by direct contact with urine from an infected animal.  Others are infected by contact with water or soil contaminated with infected urine.  Leptospira can penetrate the soft lining of the nose, mouth, and eyelid, and can enter the body through open sores and scratches in the skin.

"Ingestion of infected urine or rodent-contaminated garbage is the most important means of transmission..."

What happens once a dog is infected?

After infection, bacteria multiply quickly in the bloodstream and then move into the tissues.  They concentrate in particularly high numbers in the liver and kidney, causing extensive damage to these organs.

About eight to ten days after infection, the dog's immune system produces a strong antibody response that quickly clears most of the Leptospira from the body.  The damage caused by the bacteria usually leads to liver failure or kidney failure, and sometimes both.  In severe infections, the damage is irreversible and quickly becomes fatal.

"Dogs usually recover from mild infections, although the time for recovery varies."

Kidney diagram

Dogs usually recover from mild infections, although the time for recovery varies. In many of these dogs, even those that appear to be well recovered, small numbers of bacteria are able to survive in the body, especially in the kidney.  This low-grade ongoing infection leads to persistent shedding of small numbers of bacteria in the urine.  Dogs that have recovered and yet still carry Leptospira in their tissues are called “carriers.”

What are the signs of leptospirosis?

Severely infected dogs show signs of lethargy, depression, loss of appetite, vomiting, fever, and increased thirst and urination.  Dogs may develop jaundice, which means the lining of the mouth and the whites of the eyes turn yellow.  In some cases there may be bleeding.  Illness typically develops quickly, sometimes in just a few days, and can be rapidly fatal. In comparison, dogs with mild infections may show little or no signs of illness and the disease may go undetected.

What tests are available to diagnose leptospirosis?

There are several tests for diagnosing leptospirosis, but the two most common are the DNA-PCR test and the Microscopic Agglutination test (MAT).  Infection can be diagnosed with either test, but each has weaknesses, and in some situations both tests may be used to reach a diagnosis.

What is the DNA-PCR test for leptospirosis?

The DNA-PCR test is a rapid test that detects the DNA of Leptospira in whole blood or urine. Urine is often the preferred sample because of the large numbers of bacteria that are usually present. The test is faster and often less expensive than the MAT.

What is the “MAT” test for leptospirosis?

The “MAT” or “Microscopic Agglutination Test” detects the presence of antibodies against Leptospira in a dog's blood. If the level of antibodies (called a "titer") is high enough or can be shown to be rising over time, then infection is confirmed.       

Can leptospirosis be treated?

Yes. Antibiotic therapy is usually highly effective in treating leptospirosis, and most dogs respond quickly once antibiotics are started. There are two phases of antibiotic treatment: the first phase quickly clears the most serious or “acute” infection from the body. The second phase clears the low-grade lingering infection found in “carrier” dogs. Your veterinarian will discuss the details of treatment with you.

"...most dogs respond quickly once antibiotics are started."

In addition to antibiotics, dogs with severe kidney or liver damage may require hospitalization for intravenous fluid treatment and other medical therapy.  The prognosis for severely infected dogs is guarded since overwhelming infection usually causes irreversible organ damage, resulting in rapid deterioration and death in spite of appropriate treatment.

Can people catch leptospirosis from dogs?

Child washing hands

Yes. Leptospirosis is a zoonotic disease, which means it can spread from animals to people. Pet owners and veterinary staff should be careful when caring for an infected dog. Precautions such as face masks, gloves, and regular hand-washing are recommended to avoid getting infected urine in the eyes, nose, or mouth, or on broken skin.  Careful disposal of soiled bedding is recommended, as well as thorough disinfection of contaminated areas. Any person feeling unwell after exposure to an infected dog should seek medical attention.

This client information sheet is based on material written by: Ernest Ward, DVM , Kristiina Ruotsalo, DVM, DVSc, ACVP & Margo S. Tant, BSc, DVM, DVSc

© Copyright  2009 & 2015 LifeLearn Inc. Used and/or modified with permission under license.

We have modified it to fit Lien Animal Clinic's views and guidelines. 2018